Specifically, his blood contains an extremely rare enzyme that can be used to treat babies dying of Rhesus disease. If you've never heard of that disease and figure it's not a big deal, well, wait for the numbers.
Harrison, being a generous type, has donated his rare, life-saving blood roughly 1,000 times over 56 years. This has saved the lives of--seriously, you're not going to believe this--over two million babies around the world.
Link - via mentalfloss
From the Upcoming ueue, submitted by nmiller.
The article does say that the smallpox in Russia is under round-the-clock security, which isn't true. Yes, the building in Atlanta where our smallpox is kept has armed guards and epic security, but it's fairly well-known that the stuff in russia isn't that well-guarded.